runtime/debug: TestStack fails when GOROOT_FINAL or GOROOT is not clean

[lacombar]

[same environment as #62620]

$ cd src
$ GOROOT_FINAL=/final/destination/ ./all.bash

[...]
ok      runtime/coverage        0.003s
allocating objects
starting gc
starting dump
done dump
--- FAIL: TestStack (0.00s)
    stack_test.go:73: found GOROOT "/src/go" from environment; checking embedded GOROOT value
    stack_test.go:116: in line "\t/final/destination/src/runtime/debug/stack.go:24 +0x5e", expected prefix "\t/final/destination//src/runtime/debug/stack.go"
    stack_test.go:117: in line "\t/final/destination/src/runtime/debug/stack_test.go:31", expected prefix "\t/final/destination//src/runtime/debug/stack_test.go"
    stack_test.go:118: in line "\t/final/destination/src/runtime/debug/stack_test.go:34", expected prefix "\t/final/destination//src/runtime/debug/stack_test.go"
    stack_test.go:119: in line "\t/final/destination/src/runtime/debug/stack_test.go:56 +0x2c", expected prefix "\t/final/destination//src/runtime/debug/stack_test.go"
    stack_test.go:120: in line "\t/final/destination/src/testing/testing.go:1595 +0xff", expected prefix "\t/final/destination//src/testing/testing.go"
FAIL
FAIL    runtime/debug   0.073s
[...]

Notice the expected prefix' double path separator, /final/destination//src/, removing the trailing / from the environment variable works.

[bcmills]

In general you need to set GOROOT_FINAL to a clean path.

That said, as of Go 1.21 there isn't much point in setting GOROOT_FINAL at all (see #62047).

[bcmills]

I wonder, though: perhaps cmd/link should call filepath.Clean or similar on the value obtained from the environment?
(https://cs.opensource.google/go/go/+/master:src/cmd/link/internal/ld/pcln.go;l=813;drc=0460c61e5fd2242d27451f527dafc4d9a098fef4)

[prattmic]

It couldn’t quite be filepath, right? A Linux build of the linker cross compiling for Windows would need to clean a Windows path. We need path/filepath/windows, etc.

[bcmills]

In theory, yes.

In practice, I don't actually know how the embedded GOROOT value interacts with cross-compilation. 😅